1. Field of the Invention
This invention relates to the general field of the production of nitriles, and specifically to the production of nitriles from corresponding carboxylic acids.
2. Description of the Prior Art
The preparation of nitriles from carboxylic acids and ammonia is well known. Catalysts which have been used include bauxite (Heinemann, et al., Industrial Engineering Chemistry, 41, 2928-31 (1949)); aluminum oxide at 200.degree.-400.degree.C (USSR Pat. No. 260,628); phosphates (Swiss Pat. No. 351,263); phosphates (German Pat. No. 1,046,015); and silica gel at 400.degree.-500.degree.C (Organic Synthesis, Vol. IV, page 62).
The above reactions are quite useful in preparing high yields of nitriles from the corresponding carboxylic acids. However, some acids, such as phthalic, isophthalic, terephthalic, benzoic, and toluic, are difficult to handle because their melting points are quite high, ca. 122.degree.-425.degree., and they tend to sublime readily from the melt. The actual physical handling of such melts, e.g., metering, pumping, transferring, etc. presents a host of problems requiring special equipment, sophisticated techniques, and constant attention.
Many of these problems could be alleviated if a suitable reaction mixture were used. This invention demonstrates that complexes formed between heterocyclic nitrogen compounds, such as pyridine, quinoline, etc., and tri-substituted amines, such as triethylamine, and carboxylic acids, are useful in overcoming these problems.
The present invention solves the problem of charging the high-melting carboxylic acids, providing thereby a process for converting both low and high-melting carboxylic acids to the corresponding nitriles, by using a carboxylic acid-nitrogenous base complex. Substantially all of the nitrogenous base can be recovered from the reaction mixture because they do not recomplex with the nitriles produced. In addition, the nitrogenous bases are selected such that they do not react with ammonia at the reaction condition.